Conventionally, a monitoring system capable of distributing pictures from a video camera and remotely controlling the angle position, i.e., the panning and tilting position, zoom magnification, and the like, of the camera is available.
A camera (or a camera and a panhead on which the camera is mounted) used in such an apparatus allows a user to perform panning, tilting, and zooming operations by sending control signals from a computer to the camera through an RS-232C cable or the like.
This conventional monitoring system has, for example, an arrangement like the one shown in FIG. 2.
Referring to FIG. 2, a camera server 202 is connected to a network 201, and a camera 203 is connected to the camera server 202. A camera client 204 is also connected to the network 201. The camera client 204 instructs the camera server 202 to control the camera, and receives and displays a picture sent from the camera server 202.
FIG. 3 schematically shows the operation screen of the camera client 204. This operation screen includes an scroll box 31 in the form of a scroll bar which is used to perform panning operation, scroll boxes 32 and 33 for tilting and zooming operations, a control right button 34 for obtaining a camera control right from the camera server, and a picture display unit 35 for displaying a picture sensed by the camera.
Referring to FIG. 2, when the user performs panning, tilting, and zooming operations on the camera client 204, the camera client 204 transmits camera parameters (e.g., panning, tilt, and zoom values) designated by the user as a control command 205 to the camera server 202 through the network 201. Upon receiving a control command 206, the camera server 202 issues a control signal 207 to the camera 203 to control the camera 203. The camera server 202 changes the state of the camera first, and then notifies all connected camera clients of the current state (panning, tilt, and zoom values and the like) of the camera as camera data 208. Each camera client receives camera data 209 and recognizes the change in the current state of the camera.
Since the camera server 202 transmits camera data to all the connected camera clients, even a camera client 210 that is not controlling the camera can receive the camera data and recognizes the change in current state of the camera.
In addition, the camera server 202 also distributes picture data to all the camera clients through the network independently of the camera data.
If a plurality of cameras are connected to one camera server, one of the cameras can be dynamically designated, and the target camera can be changed to the designated one in accordance with a request from a camera client.
Owing to the feature of allowing many users to control one camera, this conventional system is based on the idea of a control right that allows only one user to control the camera for a predetermined period of time. Each user must acquire this control right before operating the camera. Camera control commands include a control right acquisition command. This command is issued when the user presses the control right button 34 in FIG. 3.
According to the prior art described above, when the camera is controlled, only a picture is provided in accordance with the angle position of the camera, but information about the main object of the picture cannot be obtained.